Oxygen by IRMS

  • δ18O values of water and water extract samples are determined by continuous flow (CF) using a Thermo Gas Bench II interfaced to a Thermo Delta V Plus mass spectrometer. We use the method described in the Thermo GAS Bench II operating manual, ThermoQuest, Oct 1999. In brief,  20-200 μL of water (depends on the sample volume available) for both standards and samples are pipetted into 10 mL glass vials (Exetainer® , Labco Ltd., UK) and quickly sealed. The vials are then purged with 0.2% CO2 in Helium and allowed to equilibrate at room temperature for at least 48 hours. The 18O/16O value of CO2 is then determined.  Long-term external precision is ± 0.12‰. 
  • Sample size:   We recommend a sample size of at least 200 μL and preferable 1 mL of water. Different water sample volumes can be analyzed by preparing complete sets of standards and samples with the same water volume, down to 50 μL. For volumes less than 50 μL, the vials are purged first with the 0.2% COin Helium, and then the water sample is added with a syringe through the vial septa, and allowed to equilibrate for 5 days. This works well for volumes down to one drop of water (about 20 μL), after which the water all evaporates in the vial.

Please contact us directly for shipping instructions.

Use our file “Sample name form for water HD 18O” to fill in the names of each sample.